Multi-zone imaging sensor and lens array

ABSTRACT

An imaging module includes a matrix of detector elements formed on a single semiconductor substrate and configured to output electrical signals in response to optical radiation that is incident on the detector elements. A filter layer is disposed over the detector elements and includes multiple filter zones overlying different, respective, convex regions of the matrix and having different, respective passbands.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/437,977, filed Apr. 3, 2012, which claims the benefit of U.S.Provisional Patent Application 61/471,215, filed Apr. 4, 2011, which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to imaging systems, andparticularly to devices and methods for multispectral imaging.

BACKGROUND

Many imaging applications involve capturing images simultaneously inmultiple different spectral bands. For example, U.S. Patent ApplicationPublication 2010/0007717, whose disclosure is incorporated herein byreference, describes an integrated processor for three-dimensional (3D)mapping. The device described includes a first input port for receivingcolor image data from a first image sensor and a second input port forreceiving depth-related image data from a second image sensor. Thesecond image sensor typically senses an image of a pattern of infraredradiation that is projected onto an object that is to be mapped.Processing circuitry generates a depth map using the depth-related imagedata and registers the depth map with the color image data. At least oneoutput port conveys the depth map and the color image data to a hostcomputer.

In some systems, a single image sensor is used to capture multipleimages. For example, U.S. Pat. No. 7,231,069 describes amultiple-view-angle camera used in an automatic photographing apparatus,which includes a narrow view angle lens, a cylinder lens, and an imagesensor. One image sensor is used, and a wide-view-angle image and anarrow-view-angle image are projected onto the image sensor at the sametime.

As another example, U.S. Patent Application Publication 2004/0001145describes a method and apparatus for multifield image generation andprocessing, in which a camera includes a plurality of lensesconfigurable in a plurality of distinct directions. A plurality of imagesensor areas collect charge fields of the scenes focused by theplurality of lenses. Processing logic coupled with the plurality ofimage sensor areas processes independent digital images for each of theplurality of image sensor areas.

SUMMARY

Embodiments of the present invention that are described hereinbelowprovide integrated devices for use in multispectral imaging systems.

There is therefore provided, in accordance with an embodiment of theinvention, an imaging module, which includes a matrix of detectorelements formed on a single semiconductor substrate and configured tooutput electrical signals in response to optical radiation that isincident on the detector elements. A filter layer is disposed over thedetector elements and includes multiple filter zones overlyingdifferent, respective, convex regions of the matrix and havingdifferent, respective passbands.

In disclosed embodiments, the respective passbands of the filter zonesinclude an infrared passband and at least one visible passband. The atleast one visible passband may include red, green and blue passbands.Typically, the filter zones and the respective convex regions arerectangular and share a common aspect ratio. In one embodiment, thefilter zones include at least first and second zones of different,respective, first and second sizes that share the common aspect ratio.

In a disclosed embodiment, the imaging module includes a plurality ofsense amplifiers, which are formed on the substrate and are coupled toread out photocharge from the detector elements in respective columns ofthe matrix, wherein sense amplifiers that are coupled to read out thephotocharge from a first one of the convex regions have a different gainfrom the sense amplifiers that are coupled to read out the photochargefrom at least a second one of the convex regions.

In some embodiments, the module includes objective optics, which areconfigured to form respective images of a common field of view on all ofthe regions of the matrix. The filter zones may include at least firstand second zones of different, respective sizes, and the objectiveoptics may include at least first and second lenses of different,respective magnifications, which are configured to form the respectiveimages on the respective regions of the matrix that are overlaid by atleast the first and second zones. In one embodiment, the objectiveoptics include a transparent wafer, which is etched to define focusingelements for forming the respective images, and which is overlaid on thesubstrate.

There is also provided, in accordance with an embodiment of theinvention, an imaging module, which includes a matrix of detectorelements formed on a single semiconductor substrate and configured tooutput electrical signals in response to optical radiation that isincident on the detector elements. Objective optics are configured tofocus light onto the matrix of the detector elements so as to formrespective images of a common field of view on different, respectiveregions of the matrix. Multiple optical filters, which have different,respective passbands, are positioned so that each filter filters thelight that is focused onto a different, respective one of the regions.

In one embodiment, the objective optics include multiple lenses, whichare configured to form the respective images, and the filters are formedas coatings on the lenses. Additionally or alternatively, the filtersinclude filter layers overlaid on the matrix of the detector elements.Further additionally or alternatively, the optical filters include aninterference filter, which defines a narrow passband for the lightincident on one of the regions of the matrix without affecting therespective passbands of the other regions.

In an alternative embodiment, the respective passbands of the filterzones comprise a luminance passband and chrominance passbands.Additionally or alternatively, the regions of the matrix comprise atleast first and second regions of different, respective sensitivities,and the objective optics comprise at least first and second lenses ofdifferent, respective F-numbers, which are configured to form therespective images on at least the first and second regions.

In some embodiments, the imaging module includes a processor, which isconfigured to process the electrical signals output by the detectorelements in the respective regions so as to generate, based on therespective images, multispectral image data with respect to an object inthe images. In a disclosed embodiment, the respective passbands of thefilter zones include an infrared passband for a first region of thematrix and at least one visible passband for at least a second region ofthe matrix, and the processor is configured to process the image datafrom the first region in order to generate a three-dimensional (3D) mapof the field of view, and to register the 3D map with a two-dimensional(2D) image generated by at least the second region. Additionally oralternatively, the processor is configured to apply differentialdeblurring to the image data from different regions of the matrix.

There is additionally provided, in accordance with an embodiment of theinvention, a method for imaging, which includes providing a matrix ofdetector elements formed on a single semiconductor substrate andconfigured to output electrical signals in response to optical radiationthat is incident on the detector elements. A filter layer is overlaid onthe detector elements, the filter layer including multiple filter zonesoverlying different, respective, convex regions of the matrix and havingdifferent, respective passbands.

There is further provided, in accordance with an embodiment of theinvention, a method for imaging, which includes providing a matrix ofdetector elements formed on a single semiconductor substrate andconfigured to output electrical signals in response to optical radiationthat is incident on the detector elements. Objective optics are alignedto focus light onto the matrix of the detector elements so as to formrespective images of a common field of view on different, respectiveregions of the matrix. Multiple optical filters, which have different,respective passbands, are positioned so that each filter filters thelight that is focused onto a different, respective one of the regions.

There is moreover provided, in accordance with an embodiment of thepresent invention, an imaging module, which includes a matrix ofdetector elements formed on a single semiconductor substrate andconfigured to output electrical signals having a first dynamic range inresponse to optical radiation that is incident on the detector elements.Objective optics are configured to focus light onto the matrix of thedetector elements so as to form respective optical images of a commonfield of view on different, respective regions of the matrix so that theregions sense the optical images with different, respective levels ofsensitivity. A processor is configured to process the electrical signalsoutput by the detector elements in the respective regions so as togenerate a combined electronic image of the common field of view with asecond dynamic range that is greater than the first dynamic range.

In one embodiment, the objective optics include lenses having different,regions F-numbers for focusing the light onto the different, respectiveregions, wherein the F-numbers are chosen so as to provide thedifferent, respective levels of sensitivity.

There is furthermore provided, in accordance with an embodiment of thepresent invention, a method for imaging, which includes providing amatrix of detector elements formed on a single semiconductor substrateand configured to output electrical signals having a first dynamic rangein response to optical radiation that is incident on the detectorelements. Objective optics are aligned to focus light onto the matrix ofthe detector elements so as to form respective images of a common fieldof view on different, respective regions of the matrix so that theregions sense the optical images with different, respective levels ofsensitivity. The electrical signals output by the detector elements inthe respective regions are processed so as to generate a combinedelectronic image of the common field of view with a second dynamic rangethat is greater than the first dynamic range.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic frontal view of an imaging module, in accordancewith an embodiment of the present invention;

FIG. 2 is a schematic side view of the imaging module of FIG. 1;

FIG. 3 is a schematic, pictorial view of an integrated imaging module,in accordance with an embodiment of the present invention; and

FIGS. 4 and 5 are flow charts that schematically illustrate methods forimaging, in accordance with embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In the system described in U.S. Patent Application Publication2010/0007717, separate color and infrared image sensors are used ingenerating a depth map that is registered with color image data. Anembodiment of the present invention that is described hereinbelowenables both depth and color image data to be captured simultaneously bya single image sensor. More generally, embodiments of the presentinvention provide devices and methods that may be used to providecompact and inexpensive solutions for multispectral imaging.

In the disclosed embodiments, an imaging module comprises a matrix ofdetector elements, which are formed on a single semiconductor substrateand are configured to output electrical signals in response to opticalradiation that is incident on the detector elements. Objective opticscomprising multiple lenses focus light from a common field of view ontothe matrix of the detector elements, and thus form multiple, respectiveimages of this field of view side-by-side on different, correspondingregions of the matrix. A number of optical filters, with different,respective passbands, filter the light that is focused onto each regionof the matrix.

Thus, two or more different images, each in a different spectral range,are formed simultaneously on different regions of the matrix. In theembodiments described below, the spectral ranges comprise infrared andvisible light, specifically red, green and blue, but other spectralconfigurations may likewise be used and are considered to be within thescope of the present invention.

In some embodiments, a filter layer is disposed directly over the matrixof the detector elements. This filter layer comprises multiple filterzones overlying different, respective, convex regions of the matrix.Each filter zone has a different, respective passband, so that thecorresponding region of the matrix captures an image in the spectralrange defined by the passband. In the context of the present descriptionand in the claims, the term “convex” is used in the accepted sense fordescribing regions in Euclidean vector space: A region is convex if forany pair of points within the region, every point on the straight lineconnecting the points is also in the region. In embodiments of thepresent invention, this criterion requires that the set of detectorelements underlying each of the filter zones be convex in this sense andthus form a contiguous, closed region.

The regions of the matrix that capture the different images may be ofdifferent sizes, and the objective optics may then comprise lenses ofdifferent, respective magnifications for forming the respective imageson the different regions. A processor may be coupled to process theelectrical signals output by the detector elements in the respectiveregions so as to generate, based on the respective images, multispectralimage data with respect to an object in the images. Because the imagesin the different spectral ranges are all formed on the same substrate,alignment and registration of the images can be easily achieved andmaintained, notwithstanding the different image sizes.

Reference is now made to FIGS. 1 and 2, which schematically illustratean imaging module 20, in accordance with an embodiment of the presentinvention. FIG. 1 is a frontal view, while FIG. 2 is a side view.Imaging module 20 comprises a single semiconductor substrate 22, such asa silicon wafer substrate, on which a matrix of detector elements 24 isformed. The detector elements and associated control and readoutcircuitry (not shown) may be produced using any suitable process knownin the art. For example, substrate 22 and detector elements 24 may beconfigured as a CCD or CMOS-type image sensor. In one embodiment, module20 is based on a commercially-available CMOS image sensor with full-HD(1920×1080) resolution, such as the OV2710 image sensor available fromOmniVision (Santa Clara, Calif.).

The matrix of detector elements 24 is overlaid by a filter layer, whichcomprises filter zones 34, 36, 38, 40, overlying respective regions 26,28, 30, 32 of the matrix. Each filter zone has a different passband; forexample, zone 34 may pass infrared light, while zones 36, 38 and 40 passred, green and blue light, respectively. Objective optics, comprisinglenses 44, 46, 48 and 50, focus light respectively through filter zones34, 36, 38, 40 onto regions 26, 28, 30, 32, and thus form an image oneach of the regions of a common field of view 52, with each such imagerepresenting a different spectral range. In this manner, module 20 maysimultaneously form infrared and color images, all of the same field ofview 52. Alternatively, in other embodiments (not shown in the figures),a similar effect may be obtained by forming the filters as coatings onthe corresponding lenses, or by positioning the filters at any othersuitable location in the optical path.

Imaging module 20 may advantageously be used for 3D mapping and colorimaging, as described in the above-mentioned U.S. Patent ApplicationPublication 2010/0007717, for example. As noted above, module 20 has theadvantage of providing both IR and color images within a single unit infixed registration, in contrast to systems known in the art, in whichactive alignment and registration may be required. A pattern of IRradiation is projected onto a scene of interest, and the IR image isprocessed in reconstruct a 3D map of the scene.

In pattern-based 3D mapping systems, it is generally desirable to filterincoming IR radiation with a narrowband filter, which is matched to thewavelength of the pattern projector. Filter zones 34, 36, 38, 40 thatare produced by coating a filter layer over the image sensor, however,typically have broad passbands. Therefore, in the embodiment that isillustrated in FIG. 1, an additional narrowband IR filter 54 isinterposed in the light path. Typically, filter 54 is an interferencefilter, comprising thin film layers on a transparent substrate (such asglass), designed to be transparent to visible radiation while blockingIR radiation outside a narrow band containing the projection wavelength.Thus, filter 54 narrows the IR passband of module 20 without affectingthe visible passbands.

The filter zones and corresponding regions of the matrix of detectorelements in the present example are rectangular and may be of differentsizes, as shown in FIGS. 1 and 2. In this case, the lenses willtypically have different magnifications. Specifically, in the picturedexample, lens 44 has a greater magnification than lenses 46, 48 and 50and thus forms a larger image on the correspondingly larger region 26.The lenses are aligned to ensure that all will simultaneously formfocused images of field of view 52 on the respective regions 26, 28, 30,32. This alignment is typically adjusted and tested at the time ofmanufacture, but it may be adjusted subsequently in the field.Alternatively or additionally, other optical elements, such as mirrorsand/or prisms (not shown in the figures), may be used in directing therespective images onto the different regions of the matrix of detectorelements.

Despite the different sizes of regions 26, 28, 30, 32, the regions mayshare a common aspect ratio, meaning that the ratio of height to widthis similar among the different regions. For example, using a full-HDimage sensor as described above, region 26 could comprise 1280×1080detector elements, while regions 28, 30 and 32 each comprise 640×360detector elements. (Although the aspect ratios are not precisely thesame, their similarity means that images from all the regions may beregistered with relatively minor cropping of the image from region 26.)The common aspect ratio of the regions is useful when the differentimages are to be registered with one another. This configuration may beused, for example, to provide a high-resolution IR image (such as for 3Dmapping) and a lower-resolution RGB color image, all with a 16×9 HDimage format.

Other configurations of the regions and corresponding filter zones arealso possible. For example, an image sensor and filters may beconfigured to include a larger, high-resolution luminance imaging zone(which receives the full spectrum of visible light) and smallercolor-sensitive zones. This sort of sensor may be used to create colorimages in accordance luminance/chrominance standards, such as YUV.

FIG. 3 is a schematic, pictorial view of imaging module 20, inaccordance with an integrated embodiment of the present invention. Inthis embodiment, the objective optics comprise a transparent wafer 60,which is etched to define focusing elements corresponding to lenses 44,46, 48 and 50 for forming the respective images on the different regionsof the matrix of detector elements 24 on substrate 22. Techniques forthis sort of wafer-scale optical production are known in the art. One ormore optical wafers of this sort (of which only one wafer is shown inthe figure) may be fabricated and overlaid on substrate 22 in order toachieve the desired focusing characteristics.

The photocharge accumulated by detector elements 24 is read out throughcolumn sense amplifiers 63, 64. In the pictured embodiment, amplifiers63 read out the columns of region 26 (overlaid by filter zone 34), whileamplifiers 64 read out the columns of regions 28, 30, 32 (overlaidrespectively by filter zones 36, 38, 40). Thus, the IR image signals areread out via amplifiers 63, while the RGB image signals are read out byamplifiers 64. This arrangement is advantageous, since it allows adifferent gain setting to be applied to the IR signal from that appliedto the RGB signals. In the 3D mapping applications described above, forexample, the IR image is typically faint, and amplifiers 63 maytherefore be set to a higher gain than amplifiers 64. In otherapplications, in which region 26 receives ambient IR radiation,amplifiers 63 may be set to a lower gain.

The arrangement of amplifiers 63, 64 along the edge of the image sensoris also advantageous in that it does not depart from the layout of imagesensor chips that are known in the art (other than having different,possibly adjustable gain controls for the different amplifiers).Alternatively, further sense amplifiers and readout lines may beprovided on substrate 22 to enable independent gain settings for zones28, 30 and 32, as well.

Additionally or alternatively, the relative F-numbers of lenses 44, 46,48 and 50 may be chosen so that the amount of light focused onto each ofregions 26, 28, 30, 32 is adjusted to compensate for the differentsensitivities of the regions. In other words, more light may be focusedonto the less sensitive regions, and less light onto the more sensitiveregions, thus enhancing the overall dynamic range of the imaging module.

As yet another alternative imaging module 20 may be used to implementhigh dynamic range imaging, by dividing the image sensor into moresensitive and less sensitive regions. The variation in the respectivelevels of sensitivity may be achieved by appropriate choice of thecorresponding lens F-numbers. The more sensitive region will capturedetails in the low-light parts of the image, while the less sensitiveregion will simultaneously capture high-light parts. A processorcombines the simultaneously-acquired image information from both regionsto create a single image with a dynamic range that is higher than thedynamic range of the electrical signals that are output by the detectorelements of the image sensor.

A processor 62 receives the electrical signals that are output bydetector elements 24 on substrate 22. Although FIG. 3, for the sake ofconceptual clarity, shows separate connections between processor 62 andthe different regions of the image sensor, in practice the signals fromall of the detector elements in the different regions may be read outthrough common output circuits to the processor, which then uses timinginformation to separate out the corresponding images. Furthermore,although the processor is shown in the figure as a separate unit fromthe image sensor, the processor may alternatively be formed on substrate22 alongside the matrix of detector elements.

Processor 62 typically registers the images formed on regions 26, 28, 30and 32 to generate multispectral image data with respect to objects infield of view 52. For example, processor 62 may use an infrared image,captured in region 26, of a pattern that is projected onto objects inthe field of view in order to produce a 3D map of the objects, and mayintegrate the 3D map with a color image of the objects captured byregions 28, 30 and 32. Suitable circuits and techniques for this purposeare described in the above-mentioned U.S. Patent Application Publication2010/0007717. Alternatively or additionally, processor 62 may carry outother sorts of image processing operations, as are known in the art.

As noted earlier, lenses 44, 46, 48 and 50 are designed to have the sameback focal length, but it may happen due to production tolerances thatafter module 20 is assembled, some of these lenses will be betterfocused than others. The defocus may be measured, for example, bycapturing an image of a suitable resolution target. Processor 62 maythen be programmed to compensate for the focal quality differences byapplying a deblurring algorithm to the images, with differentialdeblurring for the different regions. Algorithms that are known in theart may be used, mutatis mutandis, for this purpose. For example, in oneembodiment, processor 62 applies the Lurry-Richardson algorithm, asdescribed by Richardson in an article entitled “Bayesian-Based IterativeMethod of Image Restoration,” Journal of the Optical Society of America62:1, pages 55-59 (1972), which is incorporated herein by reference.

FIG. 4 is a flow chart that schematically illustrates a method forimaging, in accordance with an embodiment of the present invention. Atstep 70, a matrix of detector elements is formed on a singlesemiconductor substrate and configured to output electrical signals inresponse to optical radiation that is incident on the detector elements.At step 72, a filter layer is overlaid on the detector elements,comprising multiple filter zones overlying different, respective, convexregions of the matrix and having different, respective passbands. Thefilter zones define filters, such that each filter filters the lightthat is focused onto a different, respective one of the regions. At step74, objective optics are aligned to focus light onto the matrix of thedetector elements so as to form respective images of a common field ofview on different, respective regions of the matrix. Optionally, at step76, image data from a first region are processed in order to generate a3D map of the field of view. At step 78, the 3D map is registered with a2D image generated by at least a second region.

FIG. 5 is a flow chart that schematically illustrates a method forimaging, in accordance with another embodiment of the present invention.At step 80, a matrix of detector elements is formed on a singlesemiconductor substrate and configured to output electrical signalshaving a first dynamic range in response to optical radiation that isincident on the detector elements. At step 82, objective optics arealigned to focus light onto the matrix of the detector elements so as toform respective images of a common field of view on different,respective regions of the matrix so that the regions sense the opticalimages with different, respective levels of sensitivity. At step 84, theelectrical signals output by the detector elements in the respectiveregions are processed so as to generate a combined electronic image ofthe common field of view with a second dynamic range that is greaterthan the first dynamic range.

It will be appreciated that the embodiments described above are cited byway of example, and that the present invention is not limited to whathas been particularly shown and described hereinabove. Rather, the scopeof the present invention includes both combinations and subcombinationsof the various features described hereinabove, as well as variations andmodifications thereof which would occur to persons skilled in the artupon reading the foregoing description and which are not disclosed inthe prior art.

1. An imaging module, comprising: a matrix of detector elements formedon a single semiconductor substrate and configured to output electricalsignals in response to optical radiation that is incident on thedetector elements; and a filter layer, which is disposed over thedetector elements and comprises multiple filter zones overlyingdifferent, respective, convex regions of the matrix and havingdifferent, respective passbands.
 2. The imaging module according toclaim 1, wherein the respective passbands of the filter zones comprisean infrared passband and at least one visible passband.
 3. The imagingmodule according to claim 2, wherein the at least one visible passbandcomprises red, green and blue passbands.
 4. The imaging module accordingto claim 1, wherein the filter zones and the respective convex regionsare rectangular and share a common aspect ratio.
 5. The imaging moduleaccording to claim 1, wherein the imaging module comprises a pluralityof sense amplifiers, which are formed on the substrate and are coupledto read out photocharge from the detector elements in respective columnsof the matrix, wherein the sense amplifiers that are coupled to read outthe photocharge from a first one of the convex regions have a differentgain from the sense amplifiers that are coupled to read out thephotocharge from at least a second one of the convex regions.
 6. Theimaging module according to claim 1, and comprising objective optics,which are configured to form respective images of a common field of viewon all of the regions of the matrix.
 7. The imaging module according toclaim 6, wherein the filter zones comprise at least first and secondzones of different, respective sizes, and wherein the objective opticscomprise at least first and second lenses of different, respectivemagnifications, which are configured to form the respective images onthe respective regions of the matrix that are overlaid by at least thefirst and second zones.
 8. The imaging module according to claim 6,wherein the objective optics comprise a transparent wafer, which isetched to define focusing elements for forming the respective images,and which is overlaid on the substrate.
 9. The imaging module accordingto claim 6, and comprising a processor, which is configured to processthe electrical signals output by the detector elements in the respectiveregions so as to generate, based on the respective images, multispectralimage data with respect to an object in the images.
 10. An imagingmodule, comprising: a matrix of detector elements formed on a singlesemiconductor substrate and configured to output electrical signals inresponse to optical radiation that is incident on the detector elements;objective optics, which are configured to focus light onto the matrix ofthe detector elements so as to form respective images of a common fieldof view on different, respective regions of the matrix; and multipleoptical filters, which have different, respective passbands and arepositioned so that each filter filters the light that is focused onto adifferent, respective one of the regions.
 11. The imaging moduleaccording to claim 10, wherein the objective optics comprise multiplelenses, which are configured to configured to form the respectiveimages, and wherein the filters are formed as coatings on the lenses.12. The imaging module according to claim 10, wherein the filterscomprise filter layers overlaid on the matrix of the detector elements.13. The imaging module according to claim 12, wherein the opticalfilters further comprise an interference filter, which defines a narrowpassband for the light incident on one of the regions of the matrixwithout affecting the respective passbands of the other regions.
 14. Theimaging module according to claim 10, wherein the respective passbandsof the filter zones comprise an infrared passband and at least onevisible passband.
 15. The imaging module according to claim 14, whereinthe at least one visible passband comprises red, green and bluepassbands.
 16. The imaging module according to claim 10, wherein therespective passbands of the filter zones comprise a luminance passbandand chrominance passbands.
 17. The imaging module according to claim 10,wherein the regions of the matrix comprise at least first and secondregions of different, respective sensitivities, and wherein theobjective optics comprise at least first and second lenses of different,respective F-numbers, which are configured to form the respective imageson at least the first and second regions.
 18. The imaging moduleaccording to claim 10, wherein the objective optics comprise atransparent wafer, which is etched to define a plurality of lenses, andwhich is overlaid on the substrate.
 19. The imaging module according toclaim 10, and comprising a processor, which is configured to process theelectrical signals output by the detector elements in the respectiveregions so as to generate, based on the respective images, multispectralimage data with respect to an object in the images.
 20. A method forimaging, comprising: providing a matrix of detector elements formed on asingle semiconductor substrate and configured to output electricalsignals in response to optical radiation that is incident on thedetector elements; and overlaying a filter layer on the detectorelements, the filter layer comprising multiple filter zones overlyingdifferent, respective, convex regions of the matrix and havingdifferent, respective passbands.